This disclosure relates generally to presenting content to users of an online system, and more specifically to determining a duration that the content was presented to the users of the online system.
Online systems, such as social networking systems, allow users to connect to and to communicate with other users of the online system. Users may create profiles on an online system that are tied to their identities and include information about the users, such as interests and demographic information. The users may be individuals or entities such as corporations or charities. Online systems allow users to easily communicate and to share content with other online system users by providing content to an online system for presentation to other users. Content provided to an online system by a user may be declarative information provided by a user, status updates, check-ins to locations, images, photographs, videos, text data, or any other information a user wishes to share with additional users of the online system. An online system may also generate content for presentation to a user, such as content describing actions taken by other users on the online system.
Third party systems and online systems also provide content to users. For example, a third party system provides pages of content to users. Similarly, an online system provides pages of content to users. To increase exposure to and interaction with pages of content provided by third party systems or by the online system, the online system may provide its users with content items identifying pages of content. If a user accesses a content item identifying a page of content via a client device, the client device may retrieve and present the page of content to the user.
When providing content items for presentation to the online system identifying pages of content provided by a third party system, the third party system has an interest in the effectiveness of the content items in causing online system users to view or to access the pages of content. Similarly, the online system may seek to analyze effectiveness of content items provided by the online system in causing users to interact with pages of content provided by the online system. Conventionally, tracking mechanisms may be included in pages of content that are executed when the page of content is loaded by a client device and communicate an indication that the page of content was loaded to a third party system or to an online system associated with the page of content. However, these conventional tracking mechanisms provided limited information about interaction with the page of content as they simply identify that the page of content has been loaded by a client device. This limited information about interaction with the page of content provides limited information for an online system or a third party system to evaluate effectiveness of content items identifying the page of content in inciting users to engage with the page of content.